Electrically conductive glass composition containing suboxides of titanium and method of making the same



, Burnham W. King, Columbus, Ohio, and Harlan P. Tripp,

Louisville, Ky., assignors, by mesne assignments, to Diamond Alkali Company, Cleveland, Ohio, at corporation of Delaware No Drawing. Application December 19, 1955 Serial No. 554,105

10 Claims. ((11. 252-526)) This invention relates to new and improved electrically conductive compositions and to their preparation.

THE PRIOR ART There has, long been considerable interest in the production of a glass or glassy-like material which will conduct electricity sufiiciently well to render it feasible for use in many applications where the other inherent properties of glass would make it an ideal material. However, up to this time no completely satisfactory conducting glass has been available, and theproblem of providing an electrically conductive glass has remained an intriguing and difiicult one.

One type of glass heretofore investigated comprises an electrically conductive 'filrn, e.g., SnO of metallic deposit, deposited on a glass base. In some instances coated glasses of this type meet the requirements of specific problems. Another prior approach to the problem has been to admix an electrically conducting material with a glass. A further prior approach has been to replace sodium ions in various silicate glasses with lithium ions, thus to obtain a somewhat reduced resistivity. However, in the latter case, the resistivities obtained, while perhaps lower than ordinary glass, still are extremely high by comparison with metallic conductors. Other compositions, such as those containing Fe O also have been proposed.

OBJECTS OF .THIS INVENTION.

It is to the provision of a novel electrically conductive composition that the present invention is directed, a principal object being to provide an electrically'conductive glass adapted to be employed in various applications. A further object of the invention is to provide new and improved glass compositions.

A still further object of the invention is to provide new and improved, low cost glass compositions characterized by extremely low electrical resistance.

' 'These and other objects and advantages of the invention will appear more fully from the tollowing description thereof.

THE PRESENT INVENTION This invention broadly comprises compositions of matter comprising, in combination, an alkali metal oxide, silicon dioxide and at least one reduction product oftitanium dioxide, such as TiO, Ti O Ti O or the like.

More specifically, a preferred composition ofthis invention comprises, in combination, analkali metal oxide,

silicon dioxide, at least one reduction product oi titanium tes Pater O ice in, is intended to include oxides of the various alkali metals, i.e., sodium potassium, lithium, cesium and rubidium, sodium oxide (Na O) is probably the most common alkali metal oxide employed in forming various 5 glasses and is the preferred alkali metal oxide in the practice of this invention. Similarly, the expression alkaline earth metal as used herein is intended to include the various metals of column 2A of the periodic table, i.e.,

calcium, strontium, barium, magnesium, etc.

I The silicon dioxide, an essential ingredient in the practice of this invention, may comprise sand, silica flour,

comminuted silica gel, and the like.

The titanium compound or compounds embodied in compositions of this invention are selected from the reduction products of TiO such as TiO, Ti O and Ti O Ti O and TiO being preferred. Of the latter two, TiO generally provides a lower electrical resistivity. in practi either the desired titanium oxide may be incorporated per se, or, alternatively, a mixture of TiO and a reducing agent, e.g., aluminum, titanium, iron, silicon,

magnesium, chromium, calcium, strontium, barium, beryllium, zirconium, or the like, may be utilized.

Specific compositions of the invention utilizing TiO generally comprise mixtures of within the following ranges wherein the quantities indicated are in terms of'percent by weight:

Preferred 3O NarO 10-26 10-15 SiOo 33-55 32-4) 'llO 14-35 2435 1320.. 0-13 6-13 Compositions of the invention which contain Ti Q desirably are as follows:

4 Preferred 0:30 10-13 0-28 0-10 (F15 10-13 at a are 07 (3-10 sr-ss 36:40 18-45 20-25 0-5 0-5 04 vcan 0-5 it has. been found' that the foregoing composition's'are characterized by a singularly low electrical resistance and, hence, excellent conductivity, which conductivity is of an electronic nature characterized by a changing ionic 5.5 valency. under conditions at which the compositions are employed as electrical conductors. The present invention provides compositions in which ions are soluble in the glass phase while in the desired valence state. Moreover, compositions of this invention contain ionicmaterials characterizedby high chemical and vapor pressure stability. and which do not crystallize out of the glass Ph e,

APPLICATIONSOF COMPOSITIONS OF THIS e INVENTION Compositions embodying this invention may be emsignal devices for use at predetermined frequencies or wave lengths, bases for electrodeposition of metal, e.g., chromium, nickel, gold, etc., low ohmic resistors, electrical heating devices, e.g., space heaters, anti-freeze Other illustrative compositions in accordance with this invention, wherein the quantities expressed in terms of percent by weight and which are characterized by low resistances are set forth in the following examples:

and/or antifrost elements, and other applications where 5 Example 18 the inherent properties of glass render the use of electrically conductive compositions and coatings formed N z therefrom especially advantageous. PREPARATION OF COMPOSITIONS OF THIS IN- 12 3 I Generally, the preparation of compositions embody- N 2 ing the invention may be accomplished in various ways. 92 However, the presently preferred method, when reactants 2 3 355 in the powdered state are employed, comprises weighing 15 2 3 and dry mixing the raw materials, and removing any Example 20 lumps or other large particles which may be present, typically by forcing the mixture through a 20 mesh sieve. N The thus-prepared mixture or, if desired, a mixture of E 400 preformed glass and Ti0 with a reducing agent or a T1203 lower oxide of titanium, is then smelted in an inert or A1103 neutral atmosphere, as in a gas-fired furnace, at a tem- Example 21 perature sufficient to provide a mixture of the desired Na 0 13 3 fluidity. Typical smelting temperatures range from about a 1300 F. to about 3000 F. While higher temperatures, CaO and, at times, possibly lower temperatures also may be B O employed, it has been found that if temperatures substantially in excess of 3000 F. are employed, at times certain of the ingredients volatilize out of the mixture. While the individual compounds included in composia2 1 a tions of this invention may be added as such, it frequent- I Example 22 1y is convenient to incorporate commercially available Na 0 13 3 products which contain the desired constituents and to g make any necessary adjustments in composition as diccao tated by the specific application intended. For example, B 0 borax (N32B407) may be employed. Convenient sources 3 of SiO and Na O are commercially available alkali metal silicates, e.g., Na O-3S1O Na O-2S1O NazsiF6 35 Na O-3.25S1O Example 23 and/or Na O-SiO -TiO Similarly, F may be intro- Na 0 179 duced as Na SiF Similarly, as indicated hereinbefore, the desired tita- Ti 6 nium oxide can be added as such or formed in situ dur- 2 3 ing smelting. The following equations, which can be Emmple 24 carried out by heating the reactants, typically at 2500 o 2 5 F. for two hours in an argon atmosphere, indicate the s o 5 preparation of various sub-oxides of H0 using Ti as a Tizoa 5 reducing agent: Example 25 (1 TiO +Ti 2TiO 2 3TiO+Ti- 2Ti O 60 N 3) 5TiO +Ti- 2Ti O 3 9 3-8 The following examples, wherein the proportions are 12 3 indicated in terms of parts by weight, illustrate various Example 26 compositions having electrical resistivities of 200 ohm-cm. Na o 28,4 or less as measured by a Simpson Ohmeter, said ohmeter SiO 48.2 being more specifically described in U.S. Patent 2,051,399. Ti O 23.4

Example No. N310 S101 TlO, T10 Th0; Al B201 F1 B80 C30 MgO 02F; gig t ciiif' Glasses of the foregoing types may be employed in various applications where a glass characterized by relatively low resistivity is desired. As the data indicates,

the electrical conductivity varies sharply with the precise composition employed. Hence, those skilled in the art will recognize that variations of the above illustrative compositions may be made within the scope of this invention in order to meet a specific application.

Percent by weight BaO 0-15 CaO 0-10 MgO 0-5 B 0 0-19 A1 0 0-10 LiF 0-5 CaF 0-5 NagslFg One application for compositions of this invention is in the field of electrolytic electrodes. Such electrodes may comprise a glass of this invention either as a solid electrode element formed in the desired shape, as a glass coating on a metal base or, if desired, in admixture with various ceramic materials. For example, glasses of the foregoing types can be formed into electrodes by pouring the molten glass into a crucible and inserting thereinto, while molten,- a stainless steel rod. Those skilled in the art will appreciate, of course, that other forms of electrodes also may be formed. At times, particular care should be taken to match the material serving as a base or support for the glass so that the coeflicients of expansion do not differ substantially or do not otherwise cause difiiculty.

Example To illustrate the use of compositions of this invention as electrodes, the following mixtures are prepared, the quantities set forth being in terms of percent by weight:

Electrodes are prepared from compositions 1-6 above by smelting at 2700-3000 F. and casting into iron crucibles, stainless steel rods being inserted in the compositions prior to solidification, to form electrodes are about 1 inch in diameter, 1 inch long and tapered to a diameter of /6 inch at one end. The surfaces of the thus-formed glass electrodes are ground to present clean surfaces to the testing solution.

Using such electrodes, a series of experiments are conducted by placing the electrodes each in 250 ml. glass beakers with stainless steel cathodes spaced 1% inch from the glass anodes, there being about 4 square inches of immersed anode area and 15 square inches of cathode area. Employing a 25% by weight NaCl flowing solution as electrolyte, a cell voltage of 12 volts is maintained. Similar experiments are conducted, with substantially the same results, using as electrolytes, a solution comprising 10 gms. SnCl and 10 ml. HCl diluted to 200 ml., and a solution comprising 10 grns. oxalic acid and 5 ml. H SO diluted to 200 ml. During the electrolysis, a drop in amperage under the conditions employed is observed, the amperage resuming its initial values upon reversal of the current.

It is to be understood that although the invention has been described with specific reference to particular embodiments thereof, it is not to be so limited, since changes and alterations therein may be made which are 6 within the full intended scope of this invention as defined by the appended claims. a

What is claimed is:

l. A fused glass composition consistingessentially of 10-30% by weight of an alkali metal oxide, 31-58% by weight of SiO 14-45% by weight of an oxide of titanium selected'from the group consisting of TiO, Ti O Ti O and mixtures thereof, and the additional components being selected from the following group and in the amounts shown:

2. The composition of claim 1 wherein the oxide of titanium selected from said group is TiO.

3. The composition of claim 1 wherein the oxide of titanium is Ti O and the percentage thereof is within the range of 18-45% by weight.

4. The composition of claim 1 wherein the oxide of titanium selected from said group is a mixture of TiO and Ti O 5. The composition of claim 1 wherein said alkali metal oxide is sodium oxide.

6. An electrode formed of the composition of claim 1.

7. An electrode formed of the composition of claim 2.

8. An electrode formed of the composition of claim 3.

9. An electrode formed of the composition of claim 4.

10. The method of preparing an electrically conductive glass composition, said method comprising the steps of heating together at a temperature substantially within the range of 1300" and 3000 F. a comminuted dry mixture of an alkali metal oxide in an amount within the range of 10-30% by weight of said composition, silicon dioxide in an amount from 31-58% by weight of said composition, from 14% to 45% by weight of an oxide of titanium selected from the group consisting of TiO, Ti 0 Ti O and mixtures thereof, and the additional components being chosen from the group consisting of the following and in the amounts shown:

the temperature at which the components of said composition are heated within said range being sufi'icient to provide a substantially uniform molten mixture thereof,

. and cooling said molten mixture sufliciently to form a solid glass. I,

References Cited in the file of this patent UNITED STATES PATENTS 2,289,211 Ridgway July 7, 1942 2,497,235 Perley Feb. 4, 1950 2,587,916 Squier Mar. 4, 1952 2,786,819 Smith Mar. 26, 1957 OTHER REFERENCES Zapife, C. A.: Conversion of Certain Refractory Oxides to a Suboxide Form at High Temperatures," I. Am. Ceram. Soc. 27 (10), 293-98 (1944). V 

10. THE METHOD OF PREPARING AN ELECTRICALLY CONDUCTIVE GLASS COMPOSITION, SAID METHOD COMPRISING THE STEPS, OF HEATING TOGETHER AT A TEMPERATURE SUBSTANTIALLY WITHIN THE RANGE OF 1300* AND 300*F. A COMMINUTED DRY MIXTURE OF AN ALKALI METAL OXIDE IN AN AMOUNT WITHIN THE RANGE OF 10-30% BY WEIGHT OF SAID COMPOSITION, SILICON DIOXIDE IN AN AMOUNT FROM 31-58% BY WEIGHT OF SAID COMPOSITION, FROM 14% TO 45% BY WEIGHT OF AN OXIDE OF TITANIUM SELECTED FROM THE GROUP CONSISTING OF TIO, TI2O3, TI3O5, AND MIXTURES THEREOF, AND THE ADDITIONAL COMPONENTS BEING CHOSEN FROM THE GROUP CONSISTING OF THE FOLLOWING AND IN THE AMOUNTS SHOWN: 